Method and apparatus for fail safe control of an electronically controlled throttle valve of an internal combustion engine

Abstract

In a method and apparatus for fail-safe controlling an electronically-controlled throttle-type internal combustion engine, provision is made of two accelerator position sensors and two throttle position sensors. When either one of the two accelerator position sensors or either one of the two throttle position sensors fails to operate, a low-speed fail-safe operation of a minimum compensation, that is, an operation for maintaining a minimum output required for limp-home control operation of the engine, is executed and, then, a first fail-safe control operation is executed for controlling the position of the throttle valve using a value detected by the remaining sensor. Therefore, the throttle valve is not unintentionally opened, and the operation can be smoothly shifted to the first fail-safe control operation. When the operation for decelerating the engine is detected by a sensor of a system separate from the above-mentioned sensors, the first fail-safe control operation is interrupted and, instead, a second fail-safe control operation is executed for holding the throttle valve at a predetermined position in order to assure the low-speed fail-safe operation of the minimum compensation.

What we claimed are:  
     
       1. A method of fail-safe controlling an electronically-controlled throttle valve of an internal combustion engine comprising the steps of: 
       setting a target position of a throttle valve disposed in an intake system depending upon engine operation conditions inclusive of a position of an accelerator detected by one accelerator position sensor selected from two accelerator position sensors equipped to said engine;  
       operating said throttle valve to be opened and closed by an actuator so that a position of said throttle valve detected by one throttle position sensor selected from two throttle position sensors equipped to said engine reaches the target position;  
       when either one of said two accelerator position sensors or either one of said two throttle position sensors fails to operate, executing a first fail-safe control operation for controlling the position of said throttle valve by basically using a value detected by the remaining sensor; and  
       in a state where one sensor fails to operate between said two accelerator position sensors or one sensor fails to operate between said two throttle position sensors, interrupting said first fail-safe control operation and, instead, executing a second fail-safe control operation to hold said throttle valve at a predetermined position when an operation for decelerating the engine is detected by a sensor in a system separate from said sensors.  
     
     
       2. A method of fail-safe controlling an electronically-controlled throttle valve of an internal combustion engine according to claim  1 , wherein the detection of the deceleration operation of the engine by a sensor of said separate system includes a condition that the idling state of the engine is detected by an idle switch. 
     
     
       3. A method of fail-safe controlling an electronically-controlled throttle valve of an internal combustion engine according to claim  1 , wherein the detection of the deceleration operation of the engine by a sensor of said separate system includes a condition that the operation of the brake is detected by a brake switch. 
     
     
       4. A method of fail-safe controlling an electronically-controlled throttle valve of an internal combustion engine according to claim  1 , wherein said second fail-safe control operation interrupts the drive of said actuator, to hold the throttle valve at a predetermined position relying upon the balance of urging forces of two springs. 
     
     
       5. A method of fail-safe controlling an electronically-controlled throttle valve of an internal combustion engine according to claim  1 , wherein said second fail-safe control operation sets the target position of the throttle valve to the predetermined position to hold the throttle valve at the predetermined position by driving the actuator. 
     
     
       6. A method of fail-safe controlling an electronically-controlled throttle valve of an internal combustion engine according to claim  1 , wherein either one of the two accelerator position sensors or either one of the two throttle position sensors for executing said first fail-safe control operation or said second fail-safe control operation is determined to be in failure when the failure state of the sensor continues for a predetermined period of time. 
     
     
       7. A method of fail-safe controlling an electronically-controlled throttle valve of an internal combustion engine comprising the steps of: 
       setting a target position of a throttle valve disposed in an intake system depending upon engine operation conditions inclusive of a position of an accelerator detected by one accelerator position sensor selected from two accelerator position sensors equipped to said engine;  
       operating said throttle valve to be opened and closed by an actuator so that a position of said throttle valve detected by one throttle position sensor selected from two throttle position sensors equipped to said engine reaches the target position;  
       when either one of said two accelerator position sensors or either one of said two throttle position sensors fails to operate, executing a low-speed fail-safe operation of a minimum compensation, that is, an operation for maintaining a minimum output required for limp-home control operation of the engine, after said one sensor has been determined to be in failure; and  
       after executing the low-speed fail-safe operation of the minimum compensation, executing a single-failure fail-safe control operation to control the position of the throttle valve by using a value detected by the remaining sensor.  
     
     
       8. A method of fail-safe controlling an electronically-controlled throttle valve of an internal combustion engine according to claim  7 , wherein said low-speed fail-safe operation of the minimum compensation is the one in a state where the throttle valve, after the accelerator pedal is released, is near a predetermined position for compensating the fail-safe operation. 
     
     
       9. A method of fail-safe controlling an electronically-controlled throttle valve of an internal combustion engine according to claim  7 , wherein said low-speed fail-safe operation of the minimum compensation is the one in a state where the throttle valve, after the brake is operated, is near a predetermined position for compensating the fail-safe operation. 
     
     
       10. A method of fail-safe controlling an electronically-controlled throttle valve of an internal combustion engine according to claim  7 , wherein when said actuator is no longer operated, the throttle valve is held at a predetermined position for compensating the low-speed fail-safe operation of the minimum compensation relying upon a balance of urging forces of two springs. 
     
     
       11. A method of fail-safe controlling an electronically-controlled throttle valve of an internal combustion engine according to claim  7 , wherein the one sensor of the two accelerator position sensors or the one sensor of the two throttle position sensors is determined to be in failure when the failure state of said one sensor continues for a predetermined period of time. 
     
     
       12. A method of fail-safe controlling an electronically-controlled throttle valve of an internal combustion engine comprising the steps of: 
       setting a target position of a throttle valve disposed in an intake system depending upon engine operation conditions inclusive of a position of an accelerator detected by one accelerator position sensor selected from two accelerator position sensors equipped to said engine;  
       operating said throttle valve to be opened and closed by an actuator so that a position of said throttle valve detected by one throttle position sensor selected from two throttle position sensors equipped to said engine reaches the target position;  
       when either one of said two accelerator position sensors or either one of said two throttle position sensors fails to operate, executing a low-speed fail-safe operation of a minimum compensation, that is, an operation for maintaining a minimum output required for limp-home control operation of the engine, after said one sensor has been determined to be in failure;  
       after the low-speed fail-safe operation of the minimum compensation has been experienced, executing a first fail-safe control operation for controlling the position of the throttle valve by using a value detected by the remaining sensor that is normal between said two sensors; and  
       in a state where one sensor fails to operate between said two accelerator position sensors or one sensor fails to operate between said two throttle position sensors, interrupting said first fail-safe control operation and, instead, executing a second fail-safe control operation to hold said throttle valve at a predetermined position when an operation for decelerating the engine is detected by a sensor in a system separate from said sensors.  
     
     
       13. An apparatus for fail-safe controlling an electronically-controlled throttle valve of an internal combustion engine comprising: 
       two accelerator position sensors for detecting a position of an accelerator;  
       a target position setting means for setting a target position of a throttle valve disposed in an intake system depending upon engine operation conditions inclusive of the position of the accelerator detected by one accelerator position sensor selected from said two accelerator position sensors;  
       two throttle position sensors for detecting a position of said throttle valve;  
       a throttle valve drive means for opening and closing said throttle valve using an actuator, so that the position of said throttle valve detected by one throttle position sensor selected from said two throttle position sensors reaches the target position;  
       a first fail-safe means which, when either one of said two accelerator position sensors or either one of said two throttle position sensors fails to operate, controls the position of said throttle valve using a value detected by the remaining sensor; and  
       a second fail-safe means which, in a state where one sensor fails to operate between said two accelerator position sensors or one sensor fails to operate between said two throttle position sensors, interrupts the operation of said first fail-safe means to hold said throttle valve at a predetermined position when an operation for decelerating the engine is detected by a sensor in a system separate from said sensors.  
     
     
       14. An apparatus for fail-safe controlling an electronically-controlled throttle valve of an internal combustion engine according to claim  13 , wherein the sensor of said separate system includes an idle switch for detecting the idling state of the engine. 
     
     
       15. An apparatus for fail-safe controlling an electronically-controlled throttle valve of an internal combustion engine according to claim  13 , wherein the sensor of said separate system includes a brake switch for detecting the operation of the brake. 
     
     
       16. An apparatus for fail-safe controlling an electronically-controlled throttle valve of an internal combustion engine according to claim  13 , wherein said second fail-safe means interrupts the drive of said actuator, to hold the throttle valve at a predetermined position relying upon a balance of urging forces of two springs. 
     
     
       17. An apparatus for fail-safe controlling an electronically-controlled throttle valve of an internal combustion engine according to claim  13 , wherein said second fail-safe means sets the target position of the throttle valve to the predetermined position to hold the throttle valve at the predetermined position by driving the actuator. 
     
     
       18. An apparatus for fail-safe controlling an electronically-controlled throttle valve of an internal combustion engine according to claim  13 , wherein either one of the two accelerator position sensors or either one of the throttle position sensors is determined to be in failure when the failure state of the sensor continues for a predetermined period of time. 
     
     
       19. An apparatus for fail-safe controlling an electronically-controlled throttle valve of an internal combustion engine comprising: 
       two accelerator position sensors for detecting a position of an accelerator;  
       a target position setting means for setting a target position of a throttle valve disposed in an intake system depending upon engine operation conditions inclusive of the position of the accelerator detected by one accelerator position sensor selected from said two accelerator position sensors;  
       two throttle position sensors for detecting a position of said throttle valve;  
       a throttle valve drive means for opening and closing said throttle valve using an actuator, so that the position of said throttle valve detected by one throttle position sensor selected from said two throttle position sensors reaches the target position;  
       a single-failure fail-safe means which, when either one of said two accelerator position sensors or either one of said two throttle position sensors fails to operate, controls the position of said throttle valve using a value detected by the remaining sensor; and  
       a single-failure fail-safe permission means which permits the operation of said single-failure fail-safe means when a low-speed fail-safe operation of a minimum compensation, that is, an operation for maintaining a minimum output required for limp-home control operation of the engine, is executed after said one of the two accelerator position sensors or said one of the two throttle position sensors has been determined to be in failure.  
     
     
       20. An apparatus for fail-safe controlling an electronically-controlled throttle valve of an internal combustion engine according to claim  19 , wherein said low-speed fail-safe operation of the minimum compensation is the one in a state where the throttle valve, after the accelerator pedal is released, is near a predetermined position for compensating the fail-safe operation. 
     
     
       21. An apparatus for fail-safe controlling an electronically-controlled throttle valve of an internal combustion engine according to claim  19 , wherein the low-speed fail-safe operation of the minimum compensation is the one in a state where the throttle valve, after the brake is operated, is near a predetermined position for compensating the fail-safe operation. 
     
     
       22. An apparatus for fail-safe controlling an electronically-controlled throttle valve of an internal combustion engine according to claim  19 , wherein when said actuator is no longer operated, the throttle valve is held at a predetermined position for compensating the low-speed fail-safe operation of the minimum compensation relying upon a balance of urging forces of two springs. 
     
     
       23. An apparatus for fail-safe controlling an electronically-controlled throttle valve of an internal combustion engine according to claim  19 , wherein the one sensor of the two accelerator position sensors or the one sensor the two throttle position sensors is determined to be in failure when the failure state of said one sensor continues for a predetermined period of time. 
     
     
       24. An apparatus for fail-safe controlling an electronically-controlled throttle valve of an internal combustion engine comprising: 
       two accelerator position sensors for detecting a position of an accelerator;  
       a target position setting means for setting a target position of a throttle valve disposed in an intake system depending upon engine operation conditions inclusive of the position of the accelerator detected by one accelerator position sensor selected from said two accelerator position sensors;  
       two throttle position sensors for detecting a position of said throttle valve;  
       a throttle valve drive means for opening and closing said throttle valve using an actuator, so that the position of said throttle valve detected by one throttle position sensor selected from said two throttle position sensors reaches the target position;  
       a first fail-safe means which, when either one of said two accelerator position sensors or either one of said two throttle position sensors fails to operate, controls the position of said throttle valve using a value detected by the remaining sensor;  
       a first fail-safe permission means for permitting the operation of said first fail-safe means after executing the low-speed fail-safe operation of the minimum compensation after the determination of one of said two accelerator position sensors or one of said throttle position sensors to be in failure; and  
       a second fail-safe means which, in a state where one sensor fails to operate between said two accelerator position sensors or one sensor fails to operate between said two throttle position sensors, interrupts the operation of said first fail-safe means and, instead, holds said throttle valve at a predetermined position when an operation for decelerating the engine is detected by a sensor in a system separate from said sensors.